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“We found the effect of processed meat intake lowered quality and fish raised quality,” explained Dr. Myriam Afeiche from the Harvard School of Public Health (HSPH).

Dr. Afeiche, along with colleagues from Harvard University, recruited 156 men with infertility concerns who were enrolled in in vitro fertilization (IVF). Each participant and his partner were asked about their diet, including how often they ate processed meat, red meat, white meat, poultry, and fish, the Daily Mail reports. The research team found that men who ate less than half a portion of processed meat a day had 7.2 percent “normal” sperm, while men who ate half portion or more a day had just 5.5 percent.

Other health care professionals are not completely sold on the idea that lifestyle can have such a significant effect on male or female fertility. Dr. Allan Pacey, chairman of the British Fertility Society, raised issues with the study’s sample size as well as measurement of sperm.

“The relationship between diet and men’s fertility is an interesting one and there is certainly now convincing evidence that men who eat more fresh fruit and vegetables have better sperm than men who don’t,” said Dr. Pacey. “However, less is known about the fertility of men with poor diets and whether specific foods can be linked to poor sperm quality.”

Pacey did acknowledge that sufficient research exists to support the theory that processed meat can have a damaging effect on men’s health and that daily intake should be reduced. A similar study conducted at Harvard linked red meat consumption to an increased risk of cardiovascular issues and cancer mortality. The study, led by An Pan from HSPH’s Department of Nutrition, followed 37,698 men and 83,644 women for over 20 years, documenting eating habits and health statuses. Results showed that one daily serving of processed meat contributed to a 13 percent increased risk of death, while a daily serving of red meat led to a 20 percent increased mortality rate.

“Our study adds more evidence to the health risks of eating high amounts of red meat, which has been associated with type 2 diabetes, coronary heart disease, stroke, and certain cancers in other studies,” said Pan.